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G8MNY  > TECH     14.02.19 08:15l 53 Lines 2023 Bytes #8 (0) @ WW
BID : 59091_GB7CIP
Read: GUEST
Subj: 12V System Surge Protection
Path: ED1ZAC<ED1ZAC<CX2SA<GB7CIP
Sent: 190214/0701Z @:GB7CIP.#32.GBR.EURO #:59091 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                                              (Updated Nov 03)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

On 24cms ATV repeater GB3HV, we used the high current diode protectors from RS,
part No RS 239-494 (old part No now! so you will need other suppliers) which is
actually a special 15V zener diode, designed to always blow S/C when over-
powered, they can handle pulse currents of 75A. This was used even thought we
had a 30AH car battery connected as well, as we were worried about lightening
spikes to the mast on the hill top site.

THEY DID WORK
When our low voltage chopper PSU blew up some years ago, it put it's high
current 60V DC secondary rail out to the battery, blowing the series 30A bolted
in fuse, & applying 60V to all the 12V kit. The spike zeners did their job &
blew all the individual unit fuses. Only the odd unprotected control transistor
got zapped.

      SINGLE BATTERY     LOAD
          FUSE           FUSES
   oo 1 PROTECTED
  +       o blown     oo) 2  LOADS
  60V      o 30A fuse  oo)) 3
 FAILED   BATT                 
  PSU                       Z Z Z (RS 239-494)
   
        OLD FUSE ARRANEGMENT

This protection certainly saved 300 pounds of expensive 23cm silicon from
burning out!

       40A     40A     INDIVIDUAL
     CHARGE  CABLE       LOAD
      FUSE    FUSE       FUSES
   oooooo 1 PROTECTED
  +                   oo) 2  LOADS
  PSU                  oo)) 3
         BATT                  
                            Z Z Z (RS 239-494)
   
       NEW FUSE ARRANGEMENT

A different design SMPSU (2x 7V 40A in series) is now in use with extra fuses
so that there is a fuse between the PSU-Batt fuse, a another fuse battery to
load wiring, & individual unit fuses.


Why Don't U send an interesting Bul?

73 De John, G8MNY @ GB7CIP


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